Amino Acids as taxonomic markers in nitrogen fixing bacteria

Analysis by TLC of the free amino acids of several nitrogen -fixing bacteria revealed the presence of several unusual amino acids of various distribution in different species. These included acetylornithine, cystathionine, hydroxyglutamic acid, ethylasparagine, dihydroxyproline and the dipeptide, gamma-glutamyl S-methyl cysteine. The results indicate close similarities between the studied rhizobia. The results suggested that both R. trifolii 112; R. phaseoli; and R. sesbaru have a common ancestor. The presence of cystathionine, an unusual non - protein amino acid, in Azotobacter cHroococcutn and Rhizobium phaseoli possibly suggested a phylogenetic relationships between both species. The data obtained indicate the possible use of unusual amino acids for taxonomic revision of the nitrogen fixing bacteria

Incorporation of copper and lead into proteins in nitrogen fixing bacteria: Azotobacter chroococcus, Rhizobium sesbani and R lupini 282

A zotobacter chroococcum, Rhizobium sesbani and Rhizo bium lupini 282 were cultivated on modified Vincent medium supplemented with varying- concentrations of cooper and lead. The results indicate some disorder in the bacterial metabolic activities as a result of the presence of both elements. Several heavy metal containing proteins were detected in Rhizobium sesbani and Azotobacter chroococcum. The results suggested that both organisms were unable to regulate the incorporation heavy metals into proteins. However, R. lupini [282] was able to channel copper and lead via its metabolic activities. The results indicate that newly reclaimed soil should be cultivated with metal tolerant bacteria such as R. lupini [282] with nitrogen fixers host plans

Production of lipase by rhizobium japonicum

Corn oil was the best lipid substrate for lipase activity, dry weight of cell and total cell nitrogen of R. japonicum 61 A 76, whereas olive oil gave maximum lipase production for R. japonicum 311 b 136. The optimum concentration of corn and olive oils added to the production medium was 0.2% [V/V] for R. japonicum 61 A 76 and 311 b 136. DL- Aspartic acid and L-glutamic acid were the best nitrogen sources for biosynthesis of lipase, dry biomass and total nitrogen content of both J. Japonicum strains. Addition of glycine, L-cystine and DL-serine to the production medium caused a decrease in the above traits for R. japonicum 61 A 76, whereas other amino acids such as DL-serine, L- histidine HCL, DL-alaninen and L-tyrosine exhibited an inhibitory effect on lipase production and other characters for R. Japonicum 311 b 136. However, organic nitrogen sources [urea and peptone] are generally more available than inorganic nitrogen sources [ammonium nitrate and calcium nitrate] for production of lipase by both strains of R. Japonicum. The paper throws some light on R. Japonicum not only for N2 fixation but also for lipase production

Effect of cadmium compounds on growth of rhizobium sesbani and on growth and dinitrogen fixation of sesban

The present investigation was made to study the capacity of some cadmium resistant colonies [isolated from the parent culture of R. sesbani in presence of some cadmium compounds; cadmium sulfate and cadmium chloride] on growth, total amount of chlorophyll, nodulation and nitrogen fixation in Sesbania sesban plants. Results showed that the sensitivity of the parent strain of R. sesbani to Cd was more or less the same for both CaSo4 and CdCl2. In addition, the treatment with CaSo4 or CdCl2 at dose 50 mug/ml was suitable to isolate certain cadmium resistant colonies from the parent culture, whereas the higher doses of both cadmium compounds over 50 mug/ml seemed to inhibit completely growth of the parent strain. Moreover, results indicated that all Cd resistant colonies gave significant decrease in nodulation and nitrogen fixation in Sesbania plants compared with the parent strain. On the other hand, results manifested also that most Cd resistant colonies isolated caused significant decrease in dry weight of shoots, while no appreciable change was observed in both dry weight of roots and total amount of chlorophylls in Sesbania plants inoculated with the majority of Cd resistant colonies. It can be concluded that the inhibitory effect of Cd takes place through its effect on nitrogenase enzyme of R. sesbani and photosynthetic process [reduction of shoots] in Sesbania sesban plants